Salinity Impact on the Precarious Mangroves: A Biochemical Study on Some Taxa from Indian Sundarbans

The mangrove of Sundarbans eco-region lies in the delta formed by the rivers Ganges, Brahmaputra and Meghna, extends across the southern part of Bangladesh and West Bengal of India. Due elevated salinity (15-27 ppt) prevails in Indian Sundarbans that has detrimental impact on vegetation pattern leading to extinction of a few existing species like Heritiera fomes and Xylocarpus granatum. A comparative account of polymorphic expression of total leaf protein, two antioxidative enzymes (peroxidase and superoxide dismutase) and two hydrolyzing enzymes (Esterase and Acid phosphatase) were estimated both qualitatively and quantitatively from the leaves of five mangroves (viz., Bruguiera gymnorrhiza, Excoecaria agallocha, Heritiera fomes, Phoenix paludosa and Xylocarpus granatum, among which, H. fomes and X. granatum are considered as degraded and rest three are considered as natural control), from two different habitats (in situ habitat of Sundarbans and from ex situ habitat in fresh water condition) are discussed. The higher amount of total protein occurred in fresh water plants than that of their Sundarbans counterparts. The increment of total protein was ranged from 156 to 5.7%. Gel electrophoresis experiments revealed that in most of the cases there were extra numbers of protein bands expressed with relatively low molecular weight in saline habitat. A qualitative and quantitative study of four enzymes from both habitats revealed that in most of the cases, the numbers of isoforms, band intensity and enzyme concentrations were higher in saline habitat plants. PRX and SOD expressions were high in saline plants (ranged from 87-257% in the case of PRX and 83-229% in SOD). The increments were lower in Heritiera (87% in PRX, 83% in SOD) and Xylocarpus (98% in PRX, 76% in SOD) from saline habitat. EST increment was lower in Heritiera and Xylocarpus than other three taxa of saline habitat (137 and 143%, respectively, whereas other three species ranged from 169-287%). ACP increment in saline grown plants occurred ranging from 133-307%. Comparatively poor salt management ability in respect to protein degradation and antioxidative enzymes activity of Heritiera and Xylocarpus could be attributed with their gaunt existence in present days Sundarbans.